The different capabilities and restrictions of high-pressure and low-pressure die-casting processes need to be taken into account when choosing a method of production to meet your component requirements. Low-pressure die-casting accounts for around 20% of light metal casting but, the most commonly used is high-pressure die-casting which accounts for around 50% of light metal casting.
Low pressure die-casting primarily uses alloys with low melting points and allows for the production of components up to around 150 kg. The advantages are very high strength and the ability to form complex geometries, whilst maximising material usage.
The process is less suitable for very thin-walled parts where the required thickness is less than 3mm. Low pressure die-casting is also relatively slower than those components produced in high-pressure processes. Machine size will also limit the size of castings.
On the other hand, high pressure die-casting, which is most commonly carried out in soft alloys such as zinc and aluminium. The molten metal alloy is pressed into the mould under high pressure and at high speed, which allows for much quicker casting production. High-pressure can provide thinner cross-sections than any other casting process, with wall thicknesses under 0.40mm depending on the size of your component and requirements.
High-pressure casting will also provide smoother surfaces for finishing options. Surface finish depends on the quality of finish on the dies. This high-quality finish enables other coatings to be applied directly.
The disadvantage, however, is that high operating and investment costs are incurred. You also need to consider that machine size will limit casting size.
With high-pressure production, thick sections can be difficult to cast. High-pressure die-castings may also suffer from porosity, although working with your supplier there are methods to improve this. It is also worth noting that high start-up costs are only reduced by high volume production requests.
There are other casting techniques that are worth considering and discussing with your casting provider the most suitable approach to benefit your end product and desired results:
- In the sand-casting process, the alloy is poured into a mould made of sand, which must be destroyed in order to reveal the manufactured component.
- Alternatively, investment casting, which is used to manufacture very small cast parts, the moulds and models are also destroyed after the casting process.
- Gravity Die Casting, which uses a permanent metal mould but does not use high pressure to press the melt into the mould. Rather, the casting is manufactured or the mould filled by gravity.
All methods of die casting are useful for different circumstances, which means the choice comes down to the requirements of your next project.
Here at McDonald Diecasting Ltd, we will work with you on your requirements and help provide the best advice to achieve the best results for your products and components.